It's Saturday night, and the sidewalks of Polk Street are bustling. But up the hill at the corner of Clay Street, the Red Devil Lounge - the small nightclub that for 20 years played host to up-and-coming Bay Area musicians and '80s nostalgia tours - sits dark, with a note from owner Jay Siegan taped to a window saying it has "closed for good."

There's a similar sight on Market Street near Duboce Triangle, where Cafe Du Nord - a Prohibition-era speakeasy turned live music venue that for decades presented local showcases and intimate concerts by the likes of Neil Young, Mumford & Sons, and Train - shuttered its doors this year with plans to become a more refined space in light of the 200 new residences going in next door.

To music fans, the abrupt closures of two of the city's high-profile venues and rumors of changes coming to others might signal troubling times. Combined with the skyrocketing cost of living, the shrinking housing market and the rising number of noise complaints in neighborhoods that were once havens for nightlife, it certainly feels like an epidemic is brewing.

As it has in other aspects of life in San Francisco's 49 square miles, the technology boom has sent ripples through the landscape of the music scene, once a center for West Coast jazz, psychedelic rock and punk. But is the situation really that bad, or is it part of a larger, ever-changing pattern that's as much a part of Bay Area music history as the Grateful Dead?

'A new order'

"Cities regenerate themselves," says Stacy Horne, a veteran producer of the Noise Pop and Treasure Island music festivals. "That's what it's about. There's a new order that takes over and moves things in a different direction than before."

Not that there aren't any casualties. "The housing crisis is a real thing," she says. "Musicians are having to move out.

Several acts that seemed to define the Bay Area's bohemian ideals - Ty Segall, Thee Oh Sees' John Dwyer, Jessica Pratt and Bart Davenport, to name a few - have already departed for places like Los Angeles, Portland, Ore., and Austin, Texas.

San Francisco has the highest average rents in the nation, and the number of rent-controlled units has decreased by more than 1,000 in the past two fiscal years, according to a report by the city controller.

But, as history has shown, movement doesn't necessarily mean doom.

Dot-com era

For longtime residents, the changes are reminiscent of what happened almost 15 years ago during the dot-com era, when spiraling rents forced the closure of several independent venues and practice spaces including Art Explosion in the Mission District and Downtown Rehearsal near AT&T Park. The music scene suffered, but in many ways, the sense of peril made it stronger.

"If I learned anything from the first time around, it's that it's shortsighted to see this as good or bad," says Eric Shea, a veteran musician who is currently a member of the bands Sweet Chariot and Hot Lunch, as well as an employee at Pandora. "It is what it is. It's another gold rush that brings some money into the city and it takes away money for other things. As a musician, I'm really sad to see my favorite venue, Cafe Du Nord, change. As a grown man, I try to embrace the change and be thankful for what we had and look for the next thing."

Relocating in Bay Area

Many musicians who are getting crowded out of the city are moving to nearby communities rather than leaving the Bay Area. Mill Valley, Napa and Oakland have ushered in a host of live music venues in the past few years, many of them dedicated almost exclusively to homegrown music.

As familiar venues close in San Francisco, new ones open, including Brick and Mortar Music Hall and the Chapel in the Mission District; Neck of the Woods in the Inner Richmond; SFJazz Center in Hayes Valley; and Vacation in the Tenderloin.

This year, Horne left the Noise Pop fold to become director of events at the Battery, an invitation-only private club opened in the Financial District by two tech millionaires. In her new role, she brings live music to startup founders, app engineers and Internet entrepreneurs.

"It's a whole new audience," Horne says. "They're not the ones frequenting the clubs, but they are excited to find out about music. It's a different way for bands to present themselves."

Rich culture

One reason many of the young tech workers flock to the city is to take advantage of the vibrant nightlife and the rich culture.

Unlike the old guard of arts lovers, which congregates largely on the Van Ness Avenue corridor for performances by the Symphony, Ballet and Opera, San Francisco's more recent arrivals are immersed in the scene at large, seeking out authentic experiences and compensating for the years of flagrant file sharing by buying expensive concert tickets, merchandise and cocktails.

"As long as you have people with money, they're willing to spend it on music," says Brian Zisk, founder and executive producer of the SFMusicTech Summit.

The tech firms' shuttle buses zipping back and forth on Valencia Street are loaded with earbud-sporting music fans, many of whom work at companies that either deal directly with the music industry or produce tools that allow independent artists to reach bigger audiences than ever before. Many of them are also aspiring musicians who play in bands and regularly book studio time at places like Different Fur and John Vanderslice's Tiny Telephone.

"The music business in the Bay Area right now is as strong as its been in the last five or six years," says Allen Scott, executive vice president of Berkeley promotion company Another Planet, which produces the Outside Lands and Treasure Island music festivals and books the Independent, Bill Graham Civic Auditorium and Oakland's Fox Theater.

"In February, at the Independent, we sold out every show but one," he says of the 500-capacity venue that helped revitalize a formerly rough stretch of Divisadero Street. "That's extraordinary. People are going out to enjoy music on a nightly basis. That trickles down to everybody - the bartenders and waiters and people parking cars."

When Another Planet started booking shows at Oakland's Fox Theater six years ago, it gave new life to the neighborhood, drawing lively crowds to hip clubs including the New Parish, Uptown, the Stork Club, Cafe Van Cleef and Duende.

Dawn Holliday, the general manager of Slim's and the Great American Music Hall nightclubs and longtime producer of the annual Hardly Strictly Bluegrass Festival, also points to signs of a thriving scene in the once-struggling 11th Street corridor and beyond. "This year, I'm going to use more local bands than ever for the festival," she says.

Innovative programs

Companies including Converse, Red Bull and Levi's have made efforts to bolster the local scene by aligning themselves with musicians through innovative, hands-on programs designed to fill in where the traditional music industry fell off.

Last year, Converse set up a temporary studio called Rubber Tracks, offered free recording time to several local bands - letting them keep ownership rights to the music - and followed up with offers to perform at its mini music festival and at its new store on Market Street, all backed by its huge promotion machine.

"From working with Converse and Scion, we made more friends and fans than if we had just gone about our routine," Shea says.

While the Bay Area hasn't turned out any major breakout stars since the mid-'90s, when Third Eye Blind, Counting Crows and Smash Mouth emerged, there's no shortage of acts that can regularly headline midsize venues and tour nationally: Two Gallants, Nicki Bluhm and the Gramblers, Tycho, G-Eazy, the Soft White Sixties and more.

"In a larger way, when you look at the way music used to be consumed, the art form carries less cultural weight now," Davenport says. "It doesn't have the power it once had. There's a reason there are no new Bob Dylans in the world. I don't think rock 'n' roll is over. It's just one of the many choices now."